Scissor hoist

ABSTRACT

A scissor hoist for dump truck beds. The hoist is especially designed to be extremely rigid and resistant to twisting forces resulting from unbalanced loading of the tilting bed.

01 ttes 1 [111 3,78,10 Qlwnnell et a1. Jan. 8, 11974 SCISSOR HOIST 2,849,255 8/1958 Pasker 298/22 J 184,161 121958 Alb t 2 [75] Inventors: Glenn L. Channell, Loveland; Blame er Son 54/8 B W. Fuller, Greeley; Kenneth R. Davisson, Severance, all of C010.

[73] Assignee: Hydraulics Unlimited Mfg. Co., Eaton, C010.

[22] Filed: Aug. 6, 1971 FOREIGN PATENTS OR APPLICATIONS 513,092 2/1955 Italy 254/124 Primary Examiner-Othell M. Simpson Assistant Examiner-Robert C. Watson [21] APPL N0Z 1 4 Att0rney-Drake, Crandell & Batchelder 52 us. (:1. 254/124, 298/22 J 51 Int. Cl 366i 3/00, B60p 1/04 [57] ABSTRACT [58] Field of Search 254/86, 88, 3 R,

A scissor hoist for dump truck beds. The hoist is especially designed to be extremely rigid and resistant to twisting forces resulting from unbalanced loading of the tilting bed.

254/120, 93 R, 93 VA, 124, 8 B; 298/22 .1

[56] References Cited UNITED STATES PATENTS 2,332,961 10/1943 Wood 298/22 J 7 Claims, 10 Drawing Figures PATENTEBJAN 8I974 mm m a INVENTORS GLENN L. CHANNELL BLAINE WFULLER B NENNE TH E! DAV/.S'SON ATTORNEYS mamz PATENTED JAN 81974 WEE? 3 BF 2 INVENTORS GLEN/V L. CHANNELL BLAINE W FULLER B KENNETH R DAV/SSON @fiw A ATTORNEYS I SCISSOR HOIST SUMMARY OF THE INVENTION The present invention is directed to hydraulically operated hoists of the type employed to elevate and lower a tilting truck bed or platform, typically but not exclusively of the type employed on farms or ranches. Hoists of the type with which the present invention is concerned are commonly called scissor hoists and have been commercially available in various forms for many years. In general, hoists of this type include two links or elongate frame assemblies, one link or frame assembly being pivotally connected at one end to the truck frame and the other link or frame assembly being pivotally connected at one end to the tilting bed or platform. The remaining two ends of the link or frame assemblies are pivotally connected to each other and an extensible hydraulic motor is coupled between the truck frame and the link or frame assembly which is coupled directly to the platform so that extension of the piston rod of the motor increases the included angle between the links or frame assemblies to swing the tilting bed or platform upwardly about its pivotal connection to the truck frame.

Because of the dimensions and configurations of conventional truck frames, the transverse width ofa link or frame assemblies is limited and, for obvious reasons, the hoist is symmetrically disposed with relationship to the longitudinal center line of the truck frame and platform. This arrangement presents a definite problem in those cases where the load carried on the bed or platform is not symmetrically distributed or balanced with reference to the longitudinal center line of the bed. Particularly in the case where there is an unbalanced load near the front end of the bed, when the bed is elevated, the front end of the bed tends to twist about the longitudinal center line, the degree of twisting being dependent upon the degree of unbalancing of the load. This twisting action is in turn imposed on the hoist at the pivotal connection between the hoist structure and tilting bed, thus causing misalignment between the transversely spaced pivot points in the hoist linkage and applying unbalanced stresses to the hoist assembly.

The hoist of the present invention is especially designed and constructed to be extremely rigid and resistant to the torsional and other forces induced by the unbalanced loading of the bed or platform with which the hoist is employed. This result is achieved primarily by constructing the hoist with two subframe assemblies, each of which takes the form of a open rectangular frame having a pair of side frame members rigidly interconnected at each end by transversely extending hinge tubes welded to the side frames. Thus, each of the two subframes is complete and rigid in and of itself.

Other objects and features of the invention will become apparent by reference to the following specification and to the drawings.

IN THE DRAWINGS FIG. 1 is a detail perspective view ofa hoist embodying the present invention installed on a tilting bed truck and showing the bed at its maximum elevation relative to the truck frame;

FIG. 2 is a top plan view of the tongue frame element of the hoist of FIG. 1 prior to final assembly;

FIG. 3 is a side elevational view of the elements of FIG. 2;

FIGS. 4 and 5 are cross-sectional views of the tongue frame taken respectively on lines 44 and 5-5 of FIG. 3;

FIG. 6 is a top plan view of the main frame assembly of the hoist of FIG. 1, showing a portion of the hydraulic motor coupled to the main frame;

FIG. 7 is a cross-sectional view of the main frame assembly taken on line 77 of FIG. 6;

FIG. 8 is an end view of the main frame assembly; and

FIGS. 9 and 10 are detailed cross-sectional views of the main frame assembly taken respectively on lines 9-9 and 10-10 of FIG. 7.

Referring first to FIG. 1, there is shown a typical installation of a scissor hoist embodying the present invention, designated generally 20, mounted upon a truck frame 22 for the purpose of raising and lowering a tilting bed 24 which is pivotally mounted upon the rearward end of truck frame 22 by a conventional pivot support, not shown. Hoist is constructed from three basic sub-assemblies: a tongue frame designated generally 26, a main frame designated generally 28, and a double acting hydraulic motor of conventional construction designated generally 30. Tongue frame 26 is mounted upon truck 22 at one end for pivotal movement about a horizontal axis at 32 by mounting structure 34 whose configuration is adapted to the particular truck frame upon which the hoist is installed. In the usual case, the mounting structure 34 will include a pair of suitably shaped brackets 36 conformed to the shape of the truck frame and fixedly secured to the frame as by bolting or welding. A stationary cylindrical shaft or tube 38 (FIG. 2) is welded at opposite ends to the two brackets 36 to define the pivotal axis 32.

At its opposite end, tongue frame 26 is pivotally connected to one end of main frame 28 as at 40, while the opposite end of main frame 28 is pivotally connected to the truck bed 24 by a bracket and shaft assembly designated generally 42.

The cylinder of hydraulic motor is mounted for pivotal movement about axis 32 by a pillow block assembly 44, while its piston rod is pivotally connected to an intermediate location on the main frame 28 by a bearing assembly 46. As indicated in FIG. I, when the piston rod of motor 30 is extended, the hoist is expanded to elevate truck bed 24. When the piston rod of motor 30 is retracted into its cylinder, main frame 28 is swung in a clockwise direction about pivot 40 while at the same time tongue frame 26 swings downwardly in a counterclockwise direction about pivot 32 to lower the bed to a horizontal position when the piston rod is fully retracted. Motor 30 is preferably a double acting motor, thus enabling powered driving of bed 24 both in raising and lowering of the bed. The bed is thus hydraulically locked in its lowered position. Control of motor 30 is normally from the truck cab by a completely conventional hydraulic control system, not shown.

Structural details of tongue from frame 26 are shown in FIGS. 2-5. Frame assembly 26 includes a pair of side plates 48 which differ from each other solely in being right or left handed. The side plates 48 are rigidly interconnected with each other at their opposite ends by hinge tubes 50 and 52, hinge tube 52 being shown separated from side plates 48 in FIGS. 2 and 3 because it is not welded in place within openings 56 in the side plates until the final assembly of tongue frame 26 with main frame 28. As best seen in the cross-sectional views of FIGS. 4 and 5, each side plate 48 is formed with a main web 58 lying in a vertical general plane and integrally connected along its lower edge to a stiffening web 60 which lies in a general plane normal to that of main web 58. As best seen in the plan view of FIG. 2, stiffening webs 60 are tapered from a maximum width at the end adjacent hinge tube 50 to a minimum width adjacent hinge tube receiving openings 56. An integral upstanding stiffening flange 62 extends along the tapered side of stiffening web 60, the flange being cut away at the narrow end of web 60 to provide clearance for hinge tube 52 and the hinge tube 80 on main frame 28. An outwardly projecting flange 66 is integrally formed along the upper edge of main web 58.

As best seen in FIG. 3, main web 58 is formed along its forward edge with a semi-circular recess 68 which receives hinge tube 50, while the forward edge 70 of stiffening web 60 underlies and is in contact with the side of hinge tube 50. Flange 62 likewise has a cutout portion 72 in its forward edge complementary in shape to hinge tube 50. Side plate 48 is fixedly secured to hinge tube 50 by weldments extending along all of the points of contact between the side plate and hinge tube.

Pillow blocks 44 are mounted for free rotation on the exterior of hinge tube 50 and are held clear of interference with side plate 48 by a pair of circumferential flanges 74 on hinge tube 50.

The structure of main frame 28 is shown in detail in FIGS. 6 through 10. Like tongue frame 26, main frame 28 is constructed with a pair of right and left handed side frame members designated generally 76 rigidly interconnected at their opposite ends by hinge tubes 78 and 80 welded to the side frame members. Each of side frame members 76 is formed from a single piece of relatively heavy sheet material. As best seen in FIG. 7, each frame member 76 includes a side web 82 of generally triangular configuration, side webs 82 lying in a vertical general plane. Stiffening web sections 84 and 86 are also each of generally triangular configurations, the sections 84 and 86 each having one edge in common and integral with an edge of the triangular side web 82. The two sections 84 and 86 are bent into respective general planes perpendicular to that of the side web and are spaced from each other by parallel side edges 88 and 90. A semicircular recess 92 (FIG. 7) in side web 82 between edges 88 and 90 fonns a recess in each side frame member 76 to receive a third hinge tube 94 which is welded in position.

As was the case with tongue frame 26, the stiffening web sections 84 and 86 are tapered in their extent away from hinge tube 94 from a maximum width at hinge tube 94 to a minimum width at the locations at which the respective sections engage and are welded to hinge tube 78 and 80. The piston rod of hydraulic motor 30 is pivotally coupled on the exterior of hinge tube 94 by a bearing assembly 46 at a location between the maximum width portions of the stiffening webs of the two side frame elements 76. As in the previous case, a pair of circumferential flanges 98 are located at the exterior of hinge tube 94 to assure smooth movement of bearing assembly 46.

As best seen in the cross-sectional views of FIGS. 9 and 10, a down turned flange 100 is integrally formed along the inclined edges of sections 84 and 86, while a channel shaped flange 102 is integrally formed along the lower edge of side web 82 to extend entirely between hinge tubes 80 and 78.

The inner diameter of hinge tube 90 is dimensioned so that it will slidably and rotatably receive hinge tube 52 of tongue frame 26. In the final assembly of the scissor hoist, hinge tube 52 of the tongue frame 26 is passed through the interior of hinge tube of main frame 28 before hinge tube 52 is seated within openings 56 in the side plate 48 of tongue frame 26. After the hinge tube 52 has been inserted in hinge tube 80, hinge tube 52 is placed in position in tongue frame 26 and welded to the respective side frames within openings 56. The transverse dimension of main frame 28 is such that it is slightly less than the transverse spacing between the inner surfaces of side webs 58 of tongue frame 26 so that when the hoist is in its lower position, main frame 28 is partially received within the space between the side webs 58 of tongue frame 26.

A similar technique is employed to pivotally mount hinge tube 50 on truck frame 22 and to pivotally mount hinge tube 78 on the truck bed 24.

The hoist disclosed in the drawings is extremely rigid and resistant to torsional forces exerted by unbalanced loading of the truck bed. Each of frames 26 and 28, when assembled, constitutes a closed rectangular frame structure which is rigid in and of itself. The employment of hinge tube interconnections for the various pivotal connections of the hoist combined with the structural configuration of the side frame elements spreads the applied forces over a larger area and achieves a relatively light weight, yet extremely rigid structure.

While one embodiment of the invention has been disclosed, it will be apparent to those skilled in the art that the disclosed embodiment may be modified. Therefore, the foregoing description is to be considered exemplary rather than limiting, and the true scope of the invention is that defined in the following claims.

We claim:

1. A scissor hoist comprising a generally rectangular tongue frame having a pair of elongate longitudinally extending first side plates, first hinge tubes fixedly secured to and rigidly transversely interconnecting said first side plates in spaced parallel relationship to each other at the opposite ends thereof, a generally rectangular main frame having a pair of elongate longitudinally extending second side plates, second hinge tubes fixedly secured to and rigidly transversely interconnecting said second side plates in spaced parallel relationship to each other at the opposite ends thereof, one of said first hinge tubes of said tongue frame and one of said second hinge tubes of said main frame being telescoped with each other to pivotally connect said tongue frame to said main frame, a third hinge tube on said main frame intermediate the ends thereof parallel to said second hinge tubes and laterally offset to one side of a general plane containing the axes of said second hinge tubes, hydraulic motor means having a piston rod and a cylinder, pivot means pivotally connecting said piston rod and said cylinder respectively to a central location on said third hinge tube and to a central location on the other of said first hinge tubes whereby operation of said motor means is operable to pivot said main frame and said tongue frame relative to each other, each of said side plates defining integral first and second webs with said first web lying in a gen eral plane normal to the axes of said hinge tubes and said second web extending perpendicular to said first web along substantially the entire length thereof.

2. The invention defined in claim 1 further comprising integral flange means extending along the edge of each of said first and said stiffening webs in perpendicular relationship to the respective webs.

3. The invention defined in claim 2 wherein said flange means on said first webs of said main frame project inwardly of said main frame, the first webs of said main frame being spaced from each other by a distance less than the spacing of said first webs of said tongue frame.

4. The invention defined in claim 1 wherein said pivot means comprises bearing means journalled on the exterior of the respective hinge tubes at a location midway between the ends of the tubes, a pair of circumferential flange means on said hinge tubes at opposite sides of said bearing means for restraining said bearing means axially of said tubes, said stiffening webs each having a transversely extending edge at their maximum width portion engaged with the associated hinge tube and extending axially outwardly along the hinge tube from a location adjacent the outer side of each circumferential flange, and a weldment securing each said edge to the associated hinge tube.

5. The invention defined in claim 1 wherein each of said second side plates comprises a first web of generally triangular configuration, said second and third hinge tubes being fixedly secured to said first web at the vertices of the generally triangular shaped first web, and said second web comprises first and second sec-. tions of generally triangular configuration, each of said first and second sections having one side in common with a side of said first and second sections extending in spaced parallel relation with each other axially along opposite sides of said third hinge tube, and weldments fixedly securing said second sides to said third hinge tube.

6. The invention defined in claim 5 wherein each of said first and second sections comprises a relatively short third side at the end of said common side opposite said second side, said third side extending parallel to said second side axially along the adjacent second hinge tube, and a weldment securing each third side to the adjacent second hinge tube.

7. A scissor hoist comprising a tongue frame assembly and a main frame assembly, each of said frame assemblies comprising a pair of spaced cylindrical hinge tubes of substantial rigidity, rigid side frame means welded to and extending between said pair of hinge tubes to support and maintain said hinge tubes in said spaced parallel relationship to each other, said rigid side frame means having generally open angular flanged cross-sectional configuration over substantially the entire length thereof, thereby presenting substantial resistance to forces tending to displace the axes of the pair of hinge tubes out of parallelism with each other, the hinge tube at one end of said tongue frame assembly being rotatably received within the hinge tube at one end of said main frame assembly to pivotally interconnect the frame assemblies to each other.

UNITE STATES PATENT OFFICE CERTIFICATE OF CORREQTIUN Patent No. 3 'Z8 h1 62 Dated January 8, 197

Inventor(s) Glenn L. Channell et a1.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, Line 25, after "truck" insert --frame-- Column 2, Line 58, omit "from" Column 6, Line 16, after "spaced" insert parallel- Column 6, Line 21, after "having" insert '--a- Signed and sealed this 21st day of May 1974-.

'(SEAL) Attest:

EDWARD M.FLETCHER,JR. c C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM PC1-1050 (10-69) USCOMM-DC 0O376-P69 w u. 5. GOVERNMENT 'PRINTING OFFICE I9" 0-36B334. 

1. A scissor hoist comprising a generally rectangular tongue frame having a pair of elongate longitudinally extending first side plates, first hinge tubes fixedly secured to and rigidly transversely interconnecting said first side plates in spaced parallel relationship to each other at the opposite ends thereof, a generally rectangular main frame having a pair of elongate longitudinally extending second side plates, second hinge tubes fixedly secured to and rigidly transversely interconnecting said second side plates in spaced parallel relationship to each other at the opposite ends thereof, one of said first hinge tubes of said tongue frame and one of said second hinge tubes of said main frame being telescoped with each other to pivotally connect said tongue frame to said main frame, a third hinge tube on said main frame intermediate the ends thereof parallel to said second hinge tubes and laterally offset to one side of a general plane containing the axes of said second hinge tubes, hydraulic motor means having a piston rod and a cylinder, pivot means pivotally connecting said piston rod and said cylinder respectively to a central location on said third hinge tube and to a central location on the other of said first hinge tubes whereby operation of said motor means is operable to pivot said main frame and said tongue frame relative to each other, each of said side plates defining integral first and second webs with said first web lying in a general plane normal to the axes of said hinge tubes and said second web extending perpendicular to said first web along substantially the entire length thereof.
 2. The invention defined in claim 1 further comprising integral flange means extending along the edge of each of said first and said stiffening webs in perpendicular relationship to the respective webs.
 3. The invention defined in claim 2 wherein said flange means on said first webs of said main frame project inwardly of said main frame, the first webs of said main frame being spaced from each other by a distance less than the spacing of said first webs of said tongue frame.
 4. The invention defined in claim 1 wherein said pivot means comprises bearing means journalled on the exterior of the respective hinge tubes at a location midway between the ends of the tubes, a pair of circumferential flange means on said hinge tubes at opposite sides of said bearing means for restraining said bearing means axially of said tubes, said stiffening webs each having a transversely extending edge at their maximum width portion engaged with the associated hinge tube and extending axially outwardly along the hinge tube from a location adjacent the outer side of each circumferential flange, and a weldment securing each said edge to the associated hinge tube.
 5. The invention defined in claim 1 wherein each of said second side plates comprises a first web of generally triangular configuration, said second and third hinge tubes being fixedly secured to said first web at the vertices of the generally triangular shaped first web, and said second web cOmprises first and second sections of generally triangular configuration, each of said first and second sections having one side in common with a side of said first and second sections extending in spaced parallel relation with each other axially along opposite sides of said third hinge tube, and weldments fixedly securing said second sides to said third hinge tube.
 6. The invention defined in claim 5 wherein each of said first and second sections comprises a relatively short third side at the end of said common side opposite said second side, said third side extending parallel to said second side axially along the adjacent second hinge tube, and a weldment securing each third side to the adjacent second hinge tube.
 7. A scissor hoist comprising a tongue frame assembly and a main frame assembly, each of said frame assemblies comprising a pair of spaced cylindrical hinge tubes of substantial rigidity, rigid side frame means welded to and extending between said pair of hinge tubes to support and maintain said hinge tubes in said spaced parallel relationship to each other, said rigid side frame means having generally open angular flanged cross-sectional configuration over substantially the entire length thereof, thereby presenting substantial resistance to forces tending to displace the axes of the pair of hinge tubes out of parallelism with each other, the hinge tube at one end of said tongue frame assembly being rotatably received within the hinge tube at one end of said main frame assembly to pivotally interconnect the frame assemblies to each other. 